The invention pertains to mufflers with variable acoustic properties for pulsating gases.
A muffler with variable damping characteristics for pulsating gases is known from DE 195 03 322 C. This muffler comprises a housing; a gas feed pipe leading to the housing; pipes integrated into the housing; a pressure cell with a diaphragm, a spring, a piston rod, and a pressure connection, where the ambient pressure and the spring act on the low-pressure side of the diaphragm; a pressure line, which transmits the gas pressure to the high-pressure side of the diaphragm; and a closing element for opening and closing one of the pipes. The closing element is a valve disk, which is attached to the piston rod and which, when in the resting state, closes off the end of the gas feed pipe. A special feature of the known muffler is that the pressure line is integrated into the piston rod. This rod thus has an extension, which projects into the pipe which can be closed by the valve disk. Thanks to the pressure cell with its diaphragm, even the smallest pressure differences can be used to generate whatever forces are necessary to move the closing element. The design has only a few moving parts; it is simple, reliable, and inexpensive.
It is obvious that the hot, pulsating exhaust gases heat up the closing element, the piston rod, its guide bushing, and the pressure cell. Because the pressure cell is mounted outside the housing of the muffler, it will normally be cooled by the wind. In exhaust gas systems under high thermal loads, however, this natural cooling is not always sufficient. As a result, the temperature-sensitive components, especially the piston rod, the guide bushing, and the diaphragm, can age and corrode prematurely. This is unsatisfactory.